12/5/2000Information Organization and Retrieval Database Design: Normalization and SQL University of California, Berkeley School of Information Management and Systems SIMS 202: Information Organization and Retrieval

12/5/2000Information Organization and Retrieval Review Database design Process Entity-Relationship Diagrams Designing a database

12/5/2000Information Organization and Retrieval Database Design Process Conceptual Model Logical Model External Model Conceptual requirements Conceptual requirements Conceptual requirements Conceptual requirements Application 1 Application 2Application 3Application 4 Application 2 Application 3 Application 4 External Model External Model External Model Internal Model

12/5/2000Information Organization and Retrieval ER Diagrams: Entity An Entity is an object in the real world (or even imaginary worlds) about which we want or need to maintain information –Persons (e.g.: customers in a business, employees, authors) –Things (e.g.: purchase orders, meetings, parts, companies) Employee

12/5/2000Information Organization and Retrieval ER Diagrams: Attributes Attributes are the significant properties or characteristics of an entity that help identify it and provide the information needed to interact with it or use it. (This is the Metadata for the entities.) Employee Last Middle First Name SSN Age Birthdate Projects

12/5/2000Information Organization and Retrieval ER Diagrams: Relationships Class Attends Student Part Supplies project parts Supplier Project

12/5/2000Information Organization and Retrieval ACME Widget Co. Entities Customer Invoice Employee Inventory Supplier Account Sales Rep Parts Timecard Check

12/5/2000Information Organization and Retrieval ACME Widget Co. Functional areas Ordering Inventory Supplies Shipping Personnel Payroll We will concentrate on Ordering and Inventory

12/5/2000Information Organization and Retrieval ACME Widget Ordering Normalization Orders Customer Cust# Invoice Writes Sales-Rep Invoice# Rep# Line-Item Contains Part# QuantityInvoice# Cust#

12/5/2000Information Organization and Retrieval ACME Widget ER Model Orders Customer Cust# Invoice Writes Sales-Rep Invoice# Sales Rep# Line-Item Contains Part# QuantityInvoice# Cust# Contains Part Part#Count Price Supplier Company# Ordered Part Hourly Employee ISA Emp# Wage Company# Part#Cost Supplied Part Has On-Order Supplies Company# Part#Quantity

12/5/2000Information Organization and Retrieval Mapping to a Relational Model Each entity in the ER Diagram becomes a relation. A properly normalized ER diagram will indicate where intersection relations for many-to-many mappings are needed. Relationships are indicated by common columns (or domains) in tables that are related. We will examine the tables for the Acme Widget Company derived from the ER diagram

12/5/2000Information Organization and Retrieval Employee

12/5/2000Information Organization and Retrieval Sales-Rep Hourly

12/5/2000Information Organization and Retrieval Customer

12/5/2000Information Organization and Retrieval Invoice

12/5/2000Information Organization and Retrieval Line-Item

12/5/2000Information Organization and Retrieval Part

12/5/2000Information Organization and Retrieval Joins

12/5/2000Information Organization and Retrieval Today Normalization Relational Algebra and Calculus SQL Effectiveness and Efficiency criteria for database designs Advantages and failings of DBMS technology

12/5/2000Information Organization and Retrieval Normalization Normalization theory is based on the observation that relations with certain properties are more effective in inserting, updating and deleting data than other sets of relations containing the same data Normalization is a multi-step process beginning with an “unnormalized” relation –Hospital example from Atre, S. Data Base: Structured Techniques for Design, Performance, and Management.

12/5/2000Information Organization and Retrieval Normal Forms First Normal Form (1NF) Second Normal Form (2NF) Third Normal Form (3NF) Boyce-Codd Normal Form (BCNF) Fourth Normal Form (4NF) Fifth Normal Form (5NF)

12/5/2000Information Organization and Retrieval Normalization Boyce- Codd and Higher Functional dependencyof nonkey attributes on the primary key - Atomic values only Full Functional dependencyof nonkey attributes on the primary key No transitive dependency between nonkey attributes All determinants are candidate keys - Single multivalued dependency

12/5/2000Information Organization and Retrieval Unnormalized Relations First step in normalization is to convert the data into a two-dimensional table In unnormalized relations data can repeat within a column

12/5/2000Information Organization and Retrieval Unnormalized Relation

12/5/2000Information Organization and Retrieval First Normal Form To move to First Normal Form a relation must contain only atomic values at each row and column. –No repeating groups –A column or set of columns is called a Candidate Key when its values can uniquely identify the row in the relation.

12/5/2000Information Organization and Retrieval First Normal Form

12/5/2000Information Organization and Retrieval 1NF Storage Anomalies Insertion: A new patient has not yet undergone surgery -- hence no surgeon # -- Since surgeon # is part of the key we can’t insert. Insertion: If a surgeon is newly hired and hasn’t operated yet -- there will be no way to include that person in the database. Update: If a patient comes in for a new procedure, and has moved, we need to change multiple address entries. Deletion (type 1): Deleting a patient record may also delete all info about a surgeon. Deletion (type 2): When there are functional dependencies (like side effects and drug) changing one item eliminates other information.

12/5/2000Information Organization and Retrieval Second Normal Form A relation is said to be in Second Normal Form when every nonkey attribute is fully functionally dependent on the primary key. –That is, every nonkey attribute needs the full primary key for unique identification

12/5/2000Information Organization and Retrieval Second Normal Form

12/5/2000Information Organization and Retrieval Second Normal Form

12/5/2000Information Organization and Retrieval Second Normal Form

12/5/2000Information Organization and Retrieval 1NF Storage Anomalies Removed Insertion: Can now enter new patients without surgery. Insertion: Can now enter Surgeons who haven’t operated. Deletion (type 1): If Charles Brown dies the corresponding tuples from Patient and Surgery tables can be deleted without losing information on David Rosen. Update: If John White comes in for third time, and has moved, we only need to change the Patient table

12/5/2000Information Organization and Retrieval 2NF Storage Anomalies Insertion: Cannot enter the fact that a particular drug has a particular side effect unless it is given to a patient. Deletion: If John White receives some other drug because of the penicillin rash, and a new drug and side effect are entered, we lose the information that penicillin can cause a rash Update: If drug side effects change (a new formula) we have to update multiple occurrences of side effects.

12/5/2000Information Organization and Retrieval Third Normal Form A relation is said to be in Third Normal Form if there is no transitive functional dependency between nonkey attributes –When one nonkey attribute can be determined with one or more nonkey attributes there is said to be a transitive functional dependency. The side effect column in the Surgery table is determined by the drug administered –Side effect is transitively functionally dependent on drug so Surgery is not 3NF

12/5/2000Information Organization and Retrieval Third Normal Form

12/5/2000Information Organization and Retrieval Third Normal Form

12/5/2000Information Organization and Retrieval 2NF Storage Anomalies Removed Insertion: We can now enter the fact that a particular drug has a particular side effect in the Drug relation. Deletion: If John White recieves some other drug as a result of the rash from penicillin, but the information on penicillin and rash is maintained. Update: The side effects for each drug appear only once.

12/5/2000Information Organization and Retrieval Boyce-Codd Normal Form Most 3NF relations are also BCNF relations. A 3NF relation is NOT in BCNF if: –Candidate keys in the relation are composite keys (they are not single attributes) –There is more than one candidate key in the relation, and –The keys are not disjoint, that is, some attributes in the keys are common

12/5/2000Information Organization and Retrieval Most 3NF Relations are also BCNF

12/5/2000Information Organization and Retrieval Fourth Normal Form Any relation is in Fourth Normal Form if it is BCNF and any multivalued dependencies are trivial Eliminate non-trivial multivalued dependencies by projecting into simpler tables

12/5/2000Information Organization and Retrieval Fifth Normal Form A relation is in 5NF if every join dependency in the relation is implied by the keys of the relation Implies that relations that have been decomposed in previous NF can be recombined via natural joins to recreate the original relation.

12/5/2000Information Organization and Retrieval Relational Calculus Relational Algebra provides a set of explicit operations (select, project, join, etc) that can be used to build some desired relation from the database. Relational Calculus provides a notation for formulating the definition of that desired relation in terms of the relations in the database without explicitly stating the operations to be performed SQL is based on the relational calculus.

12/5/2000Information Organization and Retrieval Relational Algebra Operations Select Project Product Union Intersect Difference Join Divide

12/5/2000Information Organization and Retrieval Select Extracts specified tuples (rows) from a specified relation (table).

12/5/2000Information Organization and Retrieval Project Extracts specified attributes(columns) from a specified relation.

12/5/2000Information Organization and Retrieval Join Builds a relation from two specified relations consisting of all possible concatenated pairs of, one from each of the two relations, such that in each pair the two tuples satisfy some condition. A1 B1 A2 B1 A3 B2 B1 C1 B2 C2 B3 C3 A1 B1 C1 A2 B1 C1 A3 B2 C2 (Natural or Inner) Join

12/5/2000Information Organization and Retrieval Outer Join Outer Joins are similar to PRODUCT -- but will leave NULLs for any row in the first table with no corresponding rows in the second. A1 B1 A2 B1 A3 B2 A4 B7 B1 C1 B2 C2 B3 C3 A1 B1 C1 A2 B1 C1 A3 B2 C2 A4 * * Outer Join

12/5/2000Information Organization and Retrieval SQL Structured Query Language SEQUEL from IBM San Jose ANSI 1992 Standard is the version used by most DBMS today (SQL92) Basic language is standardized across relational DBMSs. Each system may have proprietary extensions to standard.

12/5/2000Information Organization and Retrieval SQL Uses Database Definition and Querying –Can be used as an interactive query language –Can be imbedded in programs Relational Calculus combines Select, Project and Join operations in a single command. SELECT.

12/5/2000Information Organization and Retrieval SELECT Syntax: –SELECT [DISTINCT] attr1, attr2,…, attr3 FROM rel1 r1, rel2 r2,… rel3 r3 WHERE condition1 {AND | OR} condition2 ORDER BY attr1 [DESC], attr3 [DESC]

12/5/2000Information Organization and Retrieval SELECT Conditions = equal to a particular value >= greater than or equal to a particular value > greater than a particular value <= less than or equal to a particular value <> not equal to a particular value LIKE “*term*” (may be other wild cards in other systems) IN (“opt1”, “opt2”,…,”optn”) BETWEEN val1 AND val2 IS NULL

12/5/2000Information Organization and Retrieval Relational Algebra Selection using SELECT Syntax: –SELECT * WHERE condition1 {AND | OR} condition2

12/5/2000Information Organization and Retrieval Relational Algebra Projection using SELECT Syntax: –SELECT [DISTINCT] attr1, attr2,…, attr3 FROM rel1 r1, rel2 r2,… rel3 r3

12/5/2000Information Organization and Retrieval Relational Algebra Join using SELECT Syntax: –SELECT * FROM rel1 r1, rel2 r2 WHERE r1.linkattr = r2.linkattr

12/5/2000Information Organization and Retrieval Sorting SELECT BIOLIFE.[Common Name], BIOLIFE.[Length (cm)] FROM BIOLIFE ORDER BY BIOLIFE.[Length (cm)] DESC;

12/5/2000Information Organization and Retrieval Subqueries SELECT SITES.[Site Name], SITES.[Destination no] FROM SITES WHERE sites.[Destination no] IN (SELECT [Destination no] from DEST where [avg temp (f)] >= 78); Can be used as a form of JOIN.

12/5/2000Information Organization and Retrieval Aggregate Functions Count Avg SUM MAX MIN

12/5/2000Information Organization and Retrieval Using Aggregate functions SELECT attr1, Sum(attr2) AS name FROM tab1, tab2... GROUP BY attr1, attr3 HAVING condition;

12/5/2000Information Organization and Retrieval Using an Aggregate Function SELECT DIVECUST.Name, Sum([Price]*[qty]) AS Total FROM (DIVECUST INNER JOIN DIVEORDS ON DIVECUST.[Customer No] = DIVEORDS.[Customer No]) INNER JOIN DIVEITEM ON DIVEORDS.[Order No] = DIVEITEM.[Order No] GROUP BY DIVECUST.Name HAVING (((DIVECUST.Name) Like "*Jazdzewski"));

12/5/2000Information Organization and Retrieval GROUP BY SELECT DEST.[Destination Name], Count(*) AS Expr1 FROM DEST INNER JOIN DIVEORDS ON DEST.[Destination Name] = DIVEORDS.Destination GROUP BY DEST.[Destination Name] HAVING ((Count(*))>1); Provides a list of Destinations with the number of orders going to that destination

12/5/2000Information Organization and Retrieval Create Table CREATE TABLE table-name (attr1 attr- type PRIMARYKEY, attr2 attr- type,…,attrN attr-type); Adds a new table with the specified attributes (and types) to the database.

12/5/2000Information Organization and Retrieval Access Data Types Numeric (1, 2, 4, 8 bytes, fixed or float) Text (255 max) Memo (64000 max) Date/Time (8 bytes) Currency (8 bytes, 15 digits + 4 digits decimal) Autonumber (4 bytes) Yes/No (1 bit) OLE (limited only by disk space) Hyperlinks (up to chars)

12/5/2000Information Organization and Retrieval Access Numeric types Byte –Stores numbers from 0 to 255 (no fractions). 1 byte Integer – Stores numbers from –32,768 to 32,767 (no fractions) 2 bytes Long Integer(Default) –Stores numbers from –2,147,483,648 to 2,147,483,647 (no fractions). 4 bytes Single –Stores numbers from E38 to – E–45 for negative values and from E–45 to E38 for positive values.4 bytes Double –Stores numbers from – E308 to – E–324 for negative values and from E308 to E–324 for positive values.158 bytes Replication ID –Globally unique identifier (GUID)N/A16 bytes

12/5/2000Information Organization and Retrieval Effectiveness and Efficiency Issues for DBMS Focus on the relational model Any column in a relational database can be searched for values. To improve efficiency indexes using storage structures such as BTrees and Hashing are used But many useful functions are not indexable and require complete scans of the the database

12/5/2000Information Organization and Retrieval Example: Text Fields In conventional RDBMS, when a text field is indexed, only exact matching of the text field contents (or Greater-than and Less- than). –Can search for individual words using pattern matching, but a full scan is required. Text searching is still done best (and fastest) by specialized text search programs (Search Engines) that we will look at more later.

12/5/2000Information Organization and Retrieval Normalizing to death Normalization splits database information across multiple tables. To retrieve complete information from a normalized database, the JOIN operation must be used. JOIN tends to be expensive in terms of processing time, and very large joins are very expensive.

12/5/2000Information Organization and Retrieval Advantages of RDBMS Possible to design complex data storage and retrieval systems with ease (and without conventional programming). Support for ACID transactions –Atomic –Consistent –Independent –Durable

12/5/2000Information Organization and Retrieval Advantages of RDBMS Support for very large databases Automatic optimization of searching (when possible) RDBMS have a simple view of the database that conforms to much of the data used in businesses. Standard query language (SQL)

12/5/2000Information Organization and Retrieval Disadvantages of RDBMS Until recently, no support for complex objects such as documents, video, images, spatial or time-series data. (ORDBMS are adding support these). Often poor support for storage of complex objects. (Disassembling the car to park it in the garage) Still no efficient and effective integrated support for things like text searching within fields.